The evolution of empathizing and systemizing: assortative mating of two strong systemizers Oxfordand the Handbooks cause of autism Online

The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism Simon Baron-Cohen Oxford Handbook of Evolutionary Psychology Edited by Louise Barrett and Robin Dunbar

Print Publication Date: Apr Subject: Psychology, Cognitive Psychology, Cognitive 2007 Neuroscience Online Publication Date: Sep DOI: 10.1093/oxfordhb/9780198568308.013.0016 2012

Abstract and Keywords

This article discusses two cognitive processes, empathising and systemising, in terms of sex differences and the implications of these for evolutionary psychology. It also discusses the theory that assortative mating of two strong systemisers is a cause of autism, a neurodevelopmental condition involving empathy impairment alongside hypersystemising. Empathising is the drive to identify another person's emotions and thoughts, and to respond to these with an appropriate emotion. Empathy is a skill (or a set of skills). It defines mindreading as the ability to interpret one's own or another agent's actions as driven by mental states. The model in the article shows the ontogenesis of a theory of mind in the first four years of life, and justifies the existence of four components on the basis of developmental competence and neuropsychological dissociation.

Keywords: cognitive processes, evolutionary psychology, assortative mating, systemisers, autism, emotion, empathy, mindreading, ontogenesis, neuropsychological dissociation

16.1. Introduction

In this chapter, I discuss two cognitive processes, empathizing and systemizing, in terms of sex differences and the implications of these for evolutionary psychology. I then discuss the theory that assortative mating of two strong systemizers is a cause of autism,

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism a neurodevelopmental condition involving empathy impairment alongside hyper- systemizing.

16.2. What is empathizing?

Empathizing is the drive to identify another person's emotions and thoughts, and to respond to these with an appropriate emotion (Davis, 1994). Empathy is a skill (or a set of skills). As with any other skill, we all vary in it. In the same way that we can think about why someone is talented or average or even disabled in these other areas, so we can think about individual differences in empathy.

16.2.1. The development of empathizing: the ‘mindreading system’ (1994)

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Fig. 16.1 Baron-Cohen's (1994) model of the mindreading system. ID, Intentionality Detector; EDD, Eye Direction Detector; SAM, Shared Attention Mechanism; ToMM, Theory of Mind Mechanism. In 1994, I proposed a model to specify the neurocognitive mechanisms that comprise the ‘mindreading system’ (Baron-Cohen, 1994, 1995). Mindreading is defined as the ability to interpret one's own or another agent's actions as driven by mental states. The model was proposed in order to explain (a) ontogenesis of a theory of mind, and (b) neurocognitive dissociations that are seen in children with or without autism. The model is shown in

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism Figure 16.1 and contains four components: ID, or the Intentionality Detector; EDD, or the Eye Direction Detector; SAM, or the (p. 214) Shared Attention Mechanism; and finally ToMM, or the Theory of Mind Mechanism.

ID and EDD build ‘dyadic’ representations of simple mental states. ID automatically interprets or represents an agent's self-propelled movement as a desire or goal-directed movement, a sign of its agency, or an entity with volition (Premack, 1990). For example, ID interprets an animate-like moving shape as ‘it wants x’, or ‘it has goal y’. EDD automatically interprets or represents eyelike stimuli as ‘looking at me’ or ‘looking at something else’. That is, EDD registers that an entity with eyes can perceive. Both ID and EDD are developmentally prior to the other two mechanisms, and are active early in infancy.

SAM is developmentally more advanced and comes on line at the end of the first year of life. SAM automatically interprets or represents if the self and another agent are (or are not) perceiving the same event. SAM does this by building ‘tri-adic’ representations. For example, where ID can build the dyadic representation ‘Mother wants the cup’ and where EDD can build the dyadic representation ‘Mother sees the cup’, SAM can build the triadic representation ‘Mother sees that I see the cup’. As is apparent, triadic representations involve embedding or recursion. [A dyadic representation (‘I see a cup’) is embedded within another dyadic representation (‘Mum sees the cup’) to produce this triadic representation.] SAM takes its input from ID and EDD, and triadic representations are made out of dyadic representations. SAM typically functions from 9 to 14 months of age, and allows ‘joint attention’ behaviours such as protodeclarative pointing and gaze monitoring (Scaife and Bruner, 1975).

ToMM allows an epistemic mental state to be represented (e.g. ‘Mother thinks this cup contains water’ or ‘Mother pretends this cup contains water’), and it integrates the full set of mental state concepts (including emotions) into a theory. ToMM develops between 2 and 4 years of age, and allows pretend play (Leslie, 1987), understanding of false belief (Wimmer and Perner, 1983), and understanding of the relationships between mental states (Wellman, 1990). An example of the latter is the seeing-leads-to-knowing principle (Pratt and Bryant, 1990), where the typical 3 year old can infer that if someone has seen an event, then he will know about it.

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism

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Fig. 16.2 Baron-Cohen's (2005) model of empathizing. TED, The Emotion Detector; TESS, The Empathizing SyStem. Other abbreviations as in Figure 16.1. The model shows the ontogenesis of a theory of mind in the first 4 years of life, and justifies the existence of four components on the basis of developmental competence and neuropsychological dissociation. In terms of developmental competence, joint attention does not appear possible until 9–14 months of age, and joint attention appears to be a necessary but not sufficient condition for understanding epistemic mental states (Baron- Cohen, 1991; Baron-Cohen and Swettenham, 1996). There appears to be a developmental lag between acquiring SAM and ToMM, suggesting that these two mechanisms are dissociable. In terms of neuropsychological dissociation, congenitally blind children can ultimately develop joint (auditory or tactile) attention, using the amodal ID rather than the visual EDD route. Children with autism appear able to represent the dyadic mental states of seeing and wanting, but show delays in shared attention (Baron-Cohen, 1989b) and in understanding false belief (Baron-Cohen et al., 1985; Baron-Cohen, 1989a)—that is, in acquiring SAM and ultimately ToMM. It is this specific developmental delay that suggests that SAM is dissociable from EDD. (p. 215)

16.2.2. Short-comings of the 1994 model: the ‘empathizing system’ (2005)

The 1994 model of the mindreading system was revised in 2005 because of certain omissions and too narrow a focus. The key omission was that information about affective states, available to the infant perceptual system, had no dedicated neurocognitive

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism mechanism. In Figure 16.2, the revised model (Baron-Cohen, 2005) is shown and now includes a new fifth component: TED, or The Emotion Detector. A particular problem for any account of the distinction between autism and psychopathy is the fact that the concept of mindreading (or theory of mind) makes no reference to the affective state in the observer triggered by recognition of another's mental state. For this reason, the revised model no longer focuses on ‘mindreading’ but rather focuses on ‘empathizing’, and also includes a new sixth component, TESS, or The Empathizing SyStem. Where the 1994 mindreading system was a model of a passive observer (all the components had simple decoding functions), the 2005 empathizing system is a model of an observer impelled towards action (because an emotion is triggered in the observer which typically motivates the observer to respond to the other person).

Like the other infancy perceptual input mechanisms of ID and EDD, the new component of TED can build dyadic representations of a special kind, namely, it can represent affective states. An example would be ‘Mother—is unhappy’, or even ‘Mother—is angry— with me’. Formally, we can describe this as ‘agent—affective state—proposition’. We know that infants can represent affective states from as early as 3 months of age (Walker, 1982). As with ID, TED is amodal, in that affective information can be picked up from facial expression, or vocal intonation, ‘motherese’ being a particularly rich source of the latter (Field, 1979). Another's affective state is presumably also detectable from their touch (e.g. tense, versus relaxed), which implies that congenitally blind infants should find affective information accessible through both auditory and tactile modalities. TED allows the detection of the basic emotions (Ekman and Friesen, 1969). The development of TED is probably aided by simple imitation that is typical of infants (e.g. imitating caregiver's expressions) which in itself would facilitate emotional contagion (Meltzoff and Decety, 2003).

When SAM becomes available, at 9–14 months of age, it can receive inputs from any of the three infancy mechanisms, ID, EDD or TED. Here, we focus on how a dyadic representation of an affective state can be converted into a triadic representation by SAM. An example would be that the dyadic representation ‘Mother is unhappy’ can be converted into a triadic representation ‘I am unhappy that Mother is unhappy’, or ‘Mother is unhappy that I am unhappy’, etc. Again, as with perceptual or volitional states, SAM's triadic representations of affective states have this special embedded, or recursive, property.

ToMM is of major importance in allowing the child to represent the full range of mental states, including epistemic ones (such as false belief), and is important in allowing the child to pull mentalistic knowledge into a useful theory with which to predict behaviour (Baron-Cohen, 1995; Wellman, 1990). But TESS allows more than behavioural explanation and prediction (itself a powerful achievement). TESS allows an empathic

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism reaction to another's emotional state. This is however, not to say that these two modules do not interact. Knowledge of mental states of others made possible by ToMM could certainly influence the (p. 216) way in which an emotion is processed and/or expressed by TESS. TESS also allows for sympathy. It is this element of TESS that gives it the adaptive benefit of ensuring that organisms feel a drive to help each other.

16.2.3. Dissociations between ToMM and TESS from neuropsychiatry

Before leaving this revision of the model, it is worth discussing why the need for this has arisen. First, emotional states are an important class of mental states to detect in others, and yet the earlier model focused only on volitional, perceptual, informational, and epistemic states. Secondly, when it comes to pathology, it would appear that in autism TED may function, although its onset may be delayed (Hobson, 1986; Baron-Cohen et al., 1993, 1997c), at least in terms of detecting basic emotions. Even high-functioning people with autism or Asperger Syndrome have difficulties both in ToMM (when measured with mental-age appropriate tests) (Baron-Cohen et al., 1997a, 2001a; Happe, 1994) and TESS (Attwood, 1997; Baron-Cohen and Wheelwright, 2004; Baron-Cohen et al., 1999a,c, 2003). We discuss autism further later in the chapter. But even at this point, the evidence suggests that TED and TESS may be fractionated.

In contrast, the psychiatric condition of psychopathy may entail an intact TED and ToMM, alongside an impaired TESS. The psychopath (or sociopath) can represent that you are in pain, or that you believe he is the gas-man, thereby gaining access to your house or your credit card. The psychopath can go on to hurt you or cheat you without having the appropriate affective reaction to your affective state. In other words, he or she doesn't care about your affective state (Mealey, 1995; Blair et al., 1997). Lack of guilt or shame or compassion in the presence of another's distress are diagnostic of psychopathy (Cleckley, 1977; Hare et al., 1990). Separating TESS and ToMM thus allows a functional distinction to be drawn between the neurocognitive causes of autism and psychopathy.

16.2.4. Developmental dissociations

Developmentally, one can also distinguish TED from TESS. We know that at 3 months of age, infants can discriminate facial and vocal expressions of emotion (Walker, 1982; Trevarthen, 1989) but that it is not until about 14 months that they can respond with appropriate affect (e.g. a facial expression of concern) to another's apparent pain (Yirmiya et al., 1990) or show ‘social referencing’. Clearly, this account is incomplete inasmuch as it does not specify how many emotions TED is capable of recognizing. Our

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism recent survey of emotions identifies 412 discrete emotion concepts that are recognized by the adult English language user (Baron-Cohen et al., submitted). How many of these are recognized in the first year of life is not clear. It is also not clear exactly how empathizing changes during the second year of life. We have assumed that the same mechanism that enables social referencing at 14 months old also allows sympathy and the growth of empathy across development. This is the most parsimonious model, though it may be that future research will justify further mechanisms that affect the development of empathy.

16.3. Sex differences in empathizing—a clue to its evolutionary origins?

Many studies converge on the conclusion that there is a female superiority in empathizing. The evidence includes:

1. Sharing and turn-taking. On average, girls show more concern for fairness, whereas boys share less. In one study, boys showed 50 times more competition, whereas girls showed 20 times more turn-taking (Charlesworth and Dzur, 1987). 2. Rough-and-tumble play or ‘rough housing’ (wrestling, mock fighting, etc.). Boys do more of this than girls. Although there's a playful component, it can hurt or be intrusive, so it needs lower empathizing to carry it out (Maccoby, 1999). 3. Responding empathically to the distress of other people. Girls from 1 year old show greater concern through more sad looks, sympathetic vocalizations and comforting. More women than men also report frequently sharing the emotional distress of their friends. Women also show more comforting, even of strangers, than men do (Hoffman, 1977). (p. 217) 4. Using a ‘theory of mind’. By 3 years old, little girls are already ahead of boys in their ability to infer what people might be thinking or intending (Happe, 1995). This sex difference appears in some but not all studies (Charman et al., 2002). 5. Sensitivity to facial expressions. Women are better at decoding non-verbal communication, picking up subtle nuances from tone of voice or facial expression, or judging a person's character (Hall, 1978). 6. Questionnaires measuring empathy. Many of these find that women score higher than men (Davis, 1994). 7. Values in relationships. More women value the development of altruistic, reciprocal relationships, which by definition require empathizing. In contrast, more men value power, politics, and competition (Ahlgren and Johnson, 1979). Girls are more likely to endorse cooperative items on a questionnaire and to rate the

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism establishment of intimacy as more important than the establishment of dominance. Boys are more likely than girls to endorse competitive items and to rate social status as more important than intimacy (Knight et al., 1989). 8. Disorders of empathy (such as psychopathic personality disorder, or conduct disorder) are far more common among males (Dodge, 1980; Blair, 1995). 9. Aggression. Even in normal quantities, aggression can only occur with reduced empathizing. Here again, there is a clear sex difference. Males tend to show far more ‘direct’ aggression (pushing, hitting, punching, etc.) whereas females tend to show more ‘indirect’ (or ‘relational’, covert) aggression (gossip, exclusion, bitchy remarks, etc.). Direct aggression may require an even lower level of empathy than indirect aggression. Indirect aggression needs better mindreading skills than does direct aggression, because its impact is strategic (Crick and Grotpeter, 1995). 10. Murder. This is the ultimate example of a lack of empathy. Daly and Wilson (1988) analysed homicide records dating back over 700 years, from a range of different societies. They found that ‘male-on-male’ homicide was 30–40 times more frequent than ‘female-on-female’ homicide. 11. Establishing a ‘dominance hierarchy’. Males are quicker to establish these. This in part may reflect their lower empathizing skills, because often a hierarchy is established by one person pushing others around, to become the leader (Strayer, 1980). 12. Language style. Girls' speech is more cooperative, reciprocal, and collaborative. In concrete terms, this is also reflected in girls being able to keep a conversational exchange with a partner going for longer. When girls disagree, they are more likely to express their different opinion sensitively, in the form of a question, rather than an assertion. Boys' talk is more ‘single-voiced discourse’ (the speaker presents their own perspective alone). The female speech style is more ‘double-voiced discourse’ (girls spend more time negotiating with the other person, trying to take the other person's wishes into account) (Smith, 1985). 13. Talk about emotions. Women's conversation involves much more talk about feelings, whereas men's conversation with each other tends to be more object- or activity-focused (Tannen, 1991). 14. Parenting style. Fathers are less likely than mothers to hold their infant in a face- to-face position. Mothers are more likely to follow through the child's choice of topic in play, whilst fathers are more likely to impose their own topic. And mothers fine- tune their speech more often to match what the child can understand (Power, 1985). 15. Face preference and eye contact. From birth, females look longer at faces, and particularly at people's eyes, and males are more likely to look at inanimate objects (Connellan et al., 2001).

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism 16. Language ability. Females have also been shown to have better language ability than males. It seems likely that good empathizing would promote language development (Baron-Cohen et al., 1997b) and vice versa, so these may not be independent.

(p. 218) 16.4. Natural selection of good empathy among females?

Why might this sex difference in empathy exist? One possibility is that it reflects natural selection of empathy among females during the course of human evolution. If one considers that good empathizing would have led to better care-giving, then since care- giving can be assumed to have been primarily a female activity until very recent history, those mothers who had better empathy would have succeeded better in ‘tuning in’ to their infant offspring's pre-verbal emotional and physical needs, which may have led to a higher likelihood of the infant surviving to reproductive age. Hence, good empathy in the mother would have promoted her inclusive fitness.

A second explanation is that females with better empathy might have found it easier to socialize—chat, gossip, network—with other females, thereby being more successful in creating social support for themselves whilst engaged in being a care-giver to their infant. Social support from other females is likely also to buffer mothers from the range of life events (illness, poverty, loss, physical attack, etc.) that might otherwise threaten her ability to care for her offspring, and so increase the likelihood of her infant surviving to reproductive age, thereby increasing her inclusive fitness.

From empathizing I want now to turn to systemizing, a very different cognitive process which appears to be stronger in males.

16.5. What is ‘systemizing’?

Systemizing is a new concept. By a ‘system’ I mean something that receives inputs and delivers outputs. To systemize, one uses ‘if—then’ (correlation) rules. The brain zooms in on a detail or parameter of the system and observes how this varies. That is, it treats a feature of a particular object or event as a variable. Alternately, a person actively, or systematically, manipulates a given variable. One notes the effect(s) of operating on one single input in terms of its effects elsewhere in the system (the output). If I do x, a

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism changes to b. If z occurs, p changes to q. Systemizing therefore requires an exact eye for detail.

Systemizing involves observation of input—operation—output relationships, leading to the identification of laws to predict that event x will occur with probability p (Baron-Cohen, 2002). Some systems are 100% lawful (e.g. an electrical light switch, or a mathematical formula). Systems that are 100% lawful have zero variance, or only 1 degree of freedom, and can therefore be predicted (and controlled) 100%. A computer might be an example of a 90% lawful system: the variance is wider or there are more degrees of freedom. The social world may be only 10% lawful. This is why systemizing the social world is of little predictive value.

Systemizing involves five phases:

Phase 1: Analysis. Single observations of input and output are recorded in a standardized manner at the lowest level of detail. Phase 2: Operation. An operation is performed on the input and the change to the output is noted. Phase 3: Repetition. The same operation is repeated over and over again to test if the same pattern between input and output is obtained. Phase 4: Law derivation. A law is formulated of the form, ‘if X (operation) occurs, A (input) changes to B’. Phase 5: Confirmation/disconfirmation. If the same pattern of input—operation— output holds true for all instances, the law is retained.

If a single instance does not fit the law, Phases 2–5 are repeated leading to modification of the law, or a new law.

Systemizing non-agentive changes is effective because these are simple changes: the systems are at least moderately lawful, with narrow variance (or limited degrees of freedom). Agentive change is less suited to systemizing because the changes in the system are complex (wide variance, or many degrees of freedom).

There are at least six kinds of systems that the human brain can analyse or construct, as shown in Table 16.1. Systemizing works for phenomena that are ultimately lawful, finite, and deterministic. The explanation is exact, and its truth-value is testable. Systemizing is of almost no use for predicting moment-to-moment changes in a person's behaviour. To predict human behaviour, empathizing is required. Systemizing and empathizing are wholly different kinds of process. (p. 219)

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism Table 16.1 Main types of analysable systems

Technical systems (e.g. a computer, a musical instrument, a hammer)

Natural systems (e.g. a tide, a weather front, a plant)

Abstract systems (e.g. mathematics, a computer program, syntax)

Social systems (e.g. a political election, a legal system, a business)

Organizable systems (e.g. a taxonomy, a collection, a library)

Motoric systems (e.g. a sports technique, a performance, a musical technique)

16.6. Sex Differences in Systemizing

What is the evidence for a stronger drive to systemize in males?

1. Toy preferences. Boys are more interested than girls in toy vehicles, weapons, building blocks, and mechanical toys, all of which are open to being ‘systemized’ (Jennings, 1977). 2. Adult occupational choices. Some occupations are almost entirely male. These include metalworking, weapon making, manufacture of musical instruments, and the construction industries, such as boat building. The focus of these occupations is on creating systems (Geary, 1998). 3. Mathematics, physics, and engineering. These disciplines all require high systemizing and are largely male-dominated. The Scholastic Aptitude Math Test (SAT-M) is the mathematics part of the test administered nationally to college applicants in the United States. Males on average score 50 points higher than females on this test (Benbow, 1988). Considering only individuals who score above 700, the sex ratio is 13:1 (men to women) (Geary, 1996). 4. Constructional abilities. On average, men score higher than women in an assembly task in which people are asked to put together a 3-dimensional (3D) mechanical apparatus. Boys are also better at constructing block buildings from 2D blueprints. Lego bricks can be combined and recombined into an infinite number of systems. Boys show more interest than girls in playing with Lego. Boys as young as 3

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism years of age are also faster at copying 3D models of outsized Lego pieces. Older boys, from the age of 9 years, are better than girls at imagining what a 3D object will look like if it is laid out flat. Boys are also better at constructing a 3D structure from just an aerial and frontal view in a picture (Kimura, 1999). 5. The Water Level Task. Originally devised by the Swiss child psychologist Jean Piaget, the task involves a bottle that is tipped at an angle. Individuals are asked to predict if the water level will be horizontal or aligned with the angle of the bottle. Women more often draw the water level aligned with the tilt of the bottle and not horizontal, as is correct (Wittig and Allen, 1984). 6. The Rod and Frame Test. If people's judgment of vertical is influenced by the tilt of the frame, they are said to be ‘field dependent’, i.e. their judgment is easily swayed by extraneous input in the surrounding context. If they are not influenced by the tilt of the frame, they are said to be ‘field independent’. Most studies indicate that females are more field dependent, i.e. women are relatively more distracted by contextual cues, and they tend not to consider each variable within a system separately. They are more likely than men to state erroneously that a rod is upright if it is aligned with its frame (Witkin et al., 1954). 7. Good attention to relevant detail. This is a general feature of systemizing and is clearly a necessary part of it. Attention to relevant detail is superior in males. One measure of this is the Embedded Figures Test. On average, males are quicker and more accurate in locating a target object from a larger, complex pattern (Elliot, 1961). Males, on average, are also better at detecting a particular feature (static or moving) than are women (Voyer et al, 1995). (p. 220) 8. The Mental Rotation Test. This test provides another example in which males are quicker and more accurate. It involves systemizing because it is necessary to treat each feature in a display as a variable that can be transformed (e.g. rotated) and then to predict the output, or how it will appear after transformation (Collins and Kimura, 1997). 9. Reading maps. This is another everyday test of systemizing, because features from 3D input must be transformed to a 2D representation. In general, boys perform at a higher level than girls in map reading. Men can also learn a route by looking at a map in fewer trials than women, and they are more successful at correctly recalling greater detail about direction and distance. This observation suggests that men treat features in the map as variables that can be transformed into three dimensions. When children are asked to make a map of an area that they have only visited once, boys' maps have a more accurate layout of the features in the environment. More of the girls' maps make serious errors in the location of important landmarks. Boys tend to emphasize routes or roads, whereas girls tend to emphasize specific landmarks (the corner shop, the park, etc). These strategies of using directional cues

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism versus using landmark cues have been widely studied. The directional strategy represents an approach to understanding space as a geometric system. Similarly, the focus on roads or routes is an example of considering space in terms of another system, in this case a transportation system (Galea and Kimura, 1993). 10. Motoric systems. When people are asked to throw or catch moving objects (target-directed tasks), such as playing darts or intercepting balls flung from a launcher, males tend to perform better than females. In addition, on average men are more accurate than women in their ability to judge which of two moving objects is travelling faster (Schiff and Oldak, 1990). 11. Organizable systems. People in the Aguaruna tribe of northern Peru were asked to classify a hundred or more examples of local specimens into related species. Men's classification systems included more sub-categories (i.e. they introduced greater differentiation) and were more consistent among individuals. Interestingly, the criteria that the Aguaruna men used to decide which animals were more closely related resembled the taxonomic criteria used by Western (mostly male) biologists (Atran, 1994). Classification and organization involves systemizing because categories are predictive. With more fine-grained categories, a system will provide more accurate predictions. 12. The Systemizing Quotient. This is a questionnaire that has been tested among adults in the general population. It includes 40 items that ask about a subject's level of interest in a range of different systems that exist in the environment, including technical, abstract, and natural systems. Males score higher than females on this measure (Baron-Cohen et al., 2003). 13. Mechanics. The Physical Prediction Questionnaire (PPQ) is based on an established method for selecting applicants to study engineering. The task involves predicting which direction levers will move when an internal mechanism of cog wheels and pulleys is engaged. Men score significantly higher on this test, compared with women (Lawson et al., 2004).

Evolutionary accounts for the male advantage in systemizing include the argument that males were primarily involved in hunting and tracking of prey, and that a male who was a good systemizer would have had greater success in both using and making tools for hunting, or navigating space to explore far afield. Both could have affected a male's reproductive success. Secondly, a good systemizer would have been better placed to acquire wealth or status through being expert in making things, and wealth/status is correlated with reproductive success as a result of sexual selection.

Some might argue that socialization may have caused these sex differences in both empathizing and systemizing. Although evidence exists for differential socialization contributing to sex differences, this is unlikely to be a sufficient explanation. Connellan et

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism al. (2001) and colleagues showed that among 1-day-old babies, boys look longer at a mechanical mobile, which is a system (p. 221) with predictable laws of motion, than at a person's face, an object that is almost impossible to systemize. One-day-old girls show the opposite profile. These sex differences are therefore present very early in life.

This raises the possibility that, while culture and socialization may partly determine the development of a male brain with a stronger interest in systems or a female brain with a stronger interest in empathy, biology may also partly determine this. There is ample evidence to support both cultural determinism and biological determinism (Eagley, 1987; Gouchie and Kimura, 1991). For example, the amount of time a 1-year-old child maintains eye contact is inversely related to the prenatal level of testosterone (Lutchmaya et al., 2002). The evidence for the biological basis of sex differences in the mind is reviewed elsewhere (Baron-Cohen, 2003).

We all have both systemizing and empathizing skills. One can envisage five broad types of brain, as Table 16.2 shows. The evidence reviewed here suggests that not all men have the male brain and not all women have the female brain. Expressed differently, some women have the male brain, and some men have the female brain. My claim here is only that more males than females have a brain of type S, and more females than males have a brain of type E. Data relevant to this claim is summarized elsewhere (Goldenfeld et al., in press).

16.7. Autism: hyper-systemizing alongside impaired empathizing?

The autistic spectrum comprises four subgroups: Asperger Syndrome (AS) (Asperger, 1944; Frith, 1991), and high-, medium- and low-functioning autism (Kanner, 1943). They all share the phenotype of social difficulties and obsessional interests (American Psychological Association, 1994). In AS, the individual has normal or above-average IQ and no language delay. In the three autism sub-groups there is invariably some degree of language delay, and the level of functioning is indexed by overall IQ. These four sub- groups are known as autism spectrum conditions (ASC).

In terms of causes, the consensus is that ASC have a genetic aetiology (Bailey et al., 1995), which leads to altered brain development (Happe et al., 1996; Baron-Cohen et al., 1999b; Frith and Frith, 19991; Courchesne, 2002) affecting social and communication development and leading to the presence of unusual narrow interests and extreme

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism repetitive behaviour (American Psychological Association, 1994). We have already (p. 222) reviewed some evidence for empathy impairments in ASC (but see Baron-Cohen, 1995 for an extensive review). In the next section we review evidence for hyper- systemizing in autism, and in first-degree relatives of people with autism. Such findings are then discussed for their significance for the evolution of systemizing in the general population.

Table 16.2 The main brain types

Profile Shorthand Type of brain equation

Individuals in whom empathizing E > S Type E: more common in is more developed than females systemizing

Individuals in whom systemizing is S > E Type S: more common in more developed than empathizing males

Individuals in whom systemizing S = E ‘Balanced’ or Type B and empathizing are both equally developed

Individuals in whom systemizing is S >> E Extreme Type S: the hyper-developed while extreme male brain. More empathizing is hypo-developed common in people with an autism spectrum condition

Individuals who have hyper- E >> S Extreme Type E: the developed empathizing skills, extreme female brain while their systemizing is hypo- (postulated) developed

16.7.1. The systemizing mechanism (SM)

The hyper-systemizing theory of ASC posits that all human brains have a systemizing mechanism (SM), and that this is set at different levels in different individuals. In people

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism with ASC, the SM is set too high. The SM is like a volume control. Evidence suggests that within the general population, there are eight degrees of systemizing:

Level 1. Such individuals have little or no drive to systemize, and consequently they can cope with rapid, unlawful change. Their SM is set so low that that they hardly notice if the input is structured or not. Although this would not interfere with their ability to socialize it would lead to a lack of precision over detail when dealing with structured information. We can think of this as hypo-systemizing. Such a person would be able to cope with agentive change easily, but may be challenged when dealing with highly lawful non-agentive systems.

Levels 2 and 3. Most people have some interest in lawful non-agentive systems, and there are sex differences in this. More females in the general population have the SM set at Level 2, and more males have it set at Level 3 (see the evidence for sex differences reviewed earlier).

Level 4. This corresponds to individuals who systemize at a higher level than average. There is some evidence that above-average systemizers have more autistic traits. Thus, scientists (who by definition have the SM set above average) score higher than non- scientists on the Autism Spectrum Quotient (AQ). Mathematicians score highest of all scientists on the AQ (Baron-Cohen et al., 2001c). Parents of children with ASC also have their SM set higher than average (Baron-Cohen and Hammer, 1997; Happe et al., 2001) and have been described as having the ‘broader phenotype’ of autism. At Level 4 one would expect a person to be talented at understanding systems with moderate variance or lawfulness.

Level 5. People with AS have their SM set at Level 5: the person can easily systemize lawful systems such as calendars or train timetables (Hermelin, 2002). Experimental evidence for hyper-systemizing in AS includes the following: (i) people with AS score higher than average on the Systemizing Quotient (SQ) (Baron-Cohen et al., 2003); (ii) people with AS perform at a normal or high level on tests of intuitive physics or geometric analysis (Shah and Frith, 1983; Joliffe and Baron-Cohen, 1997; Baron-Cohen et al., 2001b; Lawson et al., 2004); (iii) people with AS can achieve extremely high levels in domains such as mathematics, physics, or computer science (Baron-Cohen et al., 1999c); (iv) people with AS have an ‘exact mind’ when it comes to art (Myers et al., 2004) and show superior attention to detail (Plaisted et al., 1998; OʼRiordan et al., 2001).

Levels 6–8. In people with high-functioning autism (HFA), the SM is set at Level 6, in those with medium-functioning autism (MFA) it is at Level 7, and in low-functioning autism (LFA) it is at the maximum setting (Level 8). Thus, people with HFA try to socialize or empathize by ‘hacking’ (i.e. systemizing) (Happe, 1994), and on the picture-

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism sequencing task they perform above average on sequences that contain temporal or physical-causal information (Baron-Cohen et al., 1986). People with MFA perform above average on the false photograph task (Leslie and Thaiss, 1992). In LFA, their obsessions cluster in the domain of systems, such as watching electric fans go round (Baron-Cohen and Wheelwright, 1999); and given a set of coloured counters, they show extreme ‘pattern imposition’ (Frith, 1970).

16.7.2. The assortative mating of two high systemizers

The evidence for systemizing being part of the phenotype for ASC includes the following: fathers and grandfathers of children with ASC are twice as likely to work in the occupation of engineering (a clear example of a systemizing occupation), compared to men in the general population (Baron-Cohen et al., 1997d). The implication is that these fathers and grandfathers have their SM set higher than average (Level 4). Students in the natural sciences (engineering, mathematics, physics) have a higher number of relatives with autism than do students (p. 223) in the humanities (Baron-Cohen et al., 1998). Mathematicians have a higher rate of AS compared to the general population, and so do their siblings (Baron-Cohen et al., in press a).

The evidence that autism could be the genetic result of having two high systemizers as parents (assortative mating) includes the following. (a) Both mothers and fathers of children with AS have been found to be strong in systemizing on the Embedded Figures Test (Baron-Cohen and Hammer, 1997). (b) Both mothers and fathers of children with autism or AS have elevated rates of systemizing occupations among their fathers (Baron- Cohen et al., 1997d). (c) Both mothers and fathers of children with autism show hyper- masculinized patterns of brain activity during a systemizing task (Baron-Cohen et al., in press b). Whether the current high rates of ASC simply reflect better recognition, growth of services, and widening of diagnostic categories to include AS, or also reflect the increased likelihood of two high systemizers having ASC children, is a question for future research.

16.8. Conclusions

This chapter has reviewed evidence that empathizing and systemizing show strong sex differences, and that these might reflect natural selection operating differently on the two sexes. Also reviewed is the evidence that individuals on the autistic spectrum, which

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism has a genetic basis, have degrees of empathizing difficulties alongside hyper-systemizing. According to the hyper-systemizing theory, autism spectrum conditions (ASC) are the result of a normative systemizing mechanism (SM)—the function of which is to serve as a change-predicting mechanism—being set too high. This theory explains why people with autism prefer either no change, or appear ‘change resistant’. It also explains their preference for systems that change in highly lawful or predictable ways (such as mathematics, repetition, objects that spin, routine, music, machines, collections). Finally, it also explains why they become disabled when faced with systems characterized by ‘complex’ or less lawful change (such as social behaviour, conversation, people's emotions, or fiction), since these cannot be easily systemized.

Whilst ASCs are disabling in the social world, hyper-systemizing can lead to talent in areas that are systemizable. For many people with ASC, their hyper-systemizing never moves beyond Phase 1: massive collection of facts and observations (lists of trains and their departure times, watching the spin-cycle of a washing machine), or Phases 2 and 3: massive repetition of behaviour (spinning a plate or the wheels of a toy car). But for those who go beyond Phase 3 to identify a law or a pattern in the data (Phases 4 and 5), this can constitute original insight. In this sense, it is likely that the genes for increased systemizing have made remarkable contributions to human history (Fitzgerald, 2000, 2002; James, 2003). Finally, the assortative mating theory proposes that the cause of ASC is the genetic combination of having two strong systemizers as parents. This theory remains to be fully tested, but if confirmed, may help to explain why the genes that can cause social disability have also been maintained in the gene pool, as they confer all the fitness advantages that strong systemizing can bring on the first-degree relatives of people with such conditions.

Acknowledgments

I am grateful for the support of the MRC and the Nancy Lurie-Marks Family Foundation during this work. Portions of this paper are taken from elsewhere (Baron-Cohen, 2005, and in press).

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Simon Baron-Cohen

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Subscriber: University of Cambridge; date: 08 March 2016 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism Professor Simon Baron-Cohen, Autism Research Centre, Psychiatry Department, Cambridge University.

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